Magnet structures that include a superconducting coil and magnetic poles have been developed for generating magnetic fields in two classes of cyclotrons (isochronous cyclotrons and synchrocyclotrons). Synchrocyclotrons, like all cyclotrons, accelerate charged particles (ions) with a high-frequency alternating voltage in an outward spiraling path from a central axis, where the ions are introduced. Synchrocyclotrons are further characterized in that the frequency of the applied electric field is adjusted as the particles are accelerated to account for relativistic increases in particle mass at increasing velocities. Synchrocyclotrons are also characterized in that they can be very compact, and their size can shrink almost cubically with increases in the magnitude of the magnetic field generated between the poles.
When the magnetic poles are magnetically saturated, a magnetic field of about 2 Tesla can be generated between the poles. The use of superconducting coils in a synchrocyclotron, however, as described in U.S. Pat. No. 4,641,057, which is incorporated herein by reference in its entirety, is reported to increase the magnetic field up to about 5 Tesla. Additional discussion of using superconducting coils in cyclotrons is provided in X. Wu, “Conceptual Design and Orbit Dynamics in a 250 MeV Superconducting Synchrocyclotron” (1990) (Ph.D. Dissertation, Michigan State University) and in J. Kim, “An Eight Tesla Superconducting Magnet for Cyclotron Studies” (1994) (Ph.D. Dissertation, Michigan State University); both of these theses are available at http://www.nscl.msu.edu/ourlab/library/publications/index.php, and both are incorporated herein by reference in their entirety.